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Full text of "The Cambridge Natural History"

EPISTERNUM  OF MAN

35

pair of similar bones in the Hamster.1     It is possible that these
are   to   be   referred   to   the   same   category.      It   has   also   been

FIG. 24.—Episternal
vestiges in. Man.
cl, Clavicle, sawn
through ; es, " epi-
sternum " (sterno-
clavicxilai1 cartilage);
l\interclavicular
ligament ; I", costo-
clavicular ligarueat ;
yn.s, manuforium
stemi ; o,st ossa
suprastemalia j r.c,
first rib ; stt ster-
num. (From. Wie-
dersheim's Structure
of Man.}

suggested that these supposed episternal rudiments are the
vestiges of a pair of cervical ribs.
The Pectoral Girdle.—The skeleton by which the fore-limb
is connected with the trunk is known as the Pectoral Girdle.
The main part of this girdle is formed by the large scapula, or
blade-bone as it is often termed. The coracoidal elements will be
dealt with later. The scapula is not firmly connected with the
backbone; it is attached merely by muscles, thus presenting a
great difference from the corresponding pelvic girdle. The reason
for this difference is not easy to understand. On the one hand
it may be pointed out that in all running animals at any rate
there is a greater need for the fixation in a particularly firm way
of the hind-limbs; but, again, in the climbing creatures both
limbs would, one might suppose, be bettered by a firm fixation. It
must be remembered, however, that in the latter case the same
result is at least partly brought about by a well-developed clavicle,
which fixes the girdle to the sternum and so to the vertebral
column by means of the ribs.
Broadly speaking, too,, the fore-limbs require a greater freedom
and variety of movement than the hind-limbs, which are supports
1  Veryl. Anat. der WirbeMJi. Leipzig, 1898, p. 497,